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OHI-Northeast | OHI Science | Citation policy

Summary

This script shows how I made the spatial regions for the Northeast assessment. The end result is a map of 10 distinct regions including state waters and offshore areas. I used a combination of shapefiles including:

  • Northeast regional planning boundary
  • US Exclusive Economic Zone
  • Ecological Production Units
  • State waters
  • State land boundaries

The final regions file is called ne_ohi_rgns and found here.

knitr::opts_chunk$set(fig.width = 10, fig.height = 8, fig.path = 'figs/',
                      echo = FALSE, message = FALSE, warning = FALSE, root.dir = "ohi-northeast")

source('~/github/ne-prep/src/R/common.R') ### an OHI-NE specific version of common.R

dir_git <- '~/github/ohi-northeast'
dir_anx <- file.path(dir_M, 'git-annex/neprep')

library(tidyverse)
library(sf)

Ecological Production Units

The EPU’s don’t encompass all of Maine’s waters up to the border with Canada. I’m using the EEZ to extend the Northernmost EPU to Canada.

US EEZ

We need to use the US EEZ to grab the tip of offshore Maine which will be added to the Scotian Shelf (and then Gulf of Maine EPU later in this script).

Now we can join the offshore region of Maine to the Scotian Shelf epu.

These look good. The next step is to intersect EPU’s with the Northeast ocean planning boundary so that we only have regions within the plan boundary.

Northeast ocean planning boundary

Intersect EPU with planning boundary

Now I need to absorb the two scotian shelf pieces into gulf of maine

We also want the region between the EPU’s and the southeastern boundary of the NE planning area to be the last offshore region.

For some reason a lot of the coastline is still there. I’m going to create a big buffer from a State Waters shapefile and then use that to erase the coast line.

State waters

We don’t want New York in the state waters shapefile anymore so we remove it here.

Now I create a buffer from state waters to remove the weird coastline issue from the offshore region.

I’m going to join this back to epu_fix and then remove state waters

Remove state waters from the EPUs since we just want these to be offshore regions.

This isn’t perfect yet - the area around long island needs to be assigned to the Mid-Atlantic Bight. I do that later on but for now I’m focusing on State waters.

Now we need to get each state their own waters and have MA split into two.

Now we combine state regions with offshore

Almost there! But I need mid-atlantic bight to be right up against NY. I’m going to take just that polygon from the epus and subtract out the State boundaries and Connecticut waters.

Crop out those pesky RI islands.

Final regions

Join MAB back to the ne_ohi_rgns, set the CRS and then add one more column, area

Looks great! I want to add another column that has area of each region

## Deleting layer `ne_ohi_rgns' using driver `ESRI Shapefile'
## Writing layer `ne_ohi_rgns' to data source `/home/afflerbach/github/ne-prep/spatial/shapefiles/ne_ohi_rgns.shp' using driver `ESRI Shapefile'
## features:       10
## fields:         3
## geometry type:  Unknown (any)